CHARGED PRICE DIFFERENT TO SHELVE PRICE

I did some shopping at Pick n Pay Durbanville Monday at 18h53. I bought amongst other things a tray of 30 Humpty Dumpty XLARGE eggs as it was priced the same as the Humpty Dumpty Large Eggs at R69.99. The eggs was packed next to each other and the price on the shelve was exactly the same. I got home and checked my slip just to see that I was charged R81.99 instead. I am very upset because this has happened a number of times at the same shop. I logged an online query yesterday, received a reference number with a promise that they will get back to me. TO date still no response. Ref nr: ***